The present invention relates to a wiper rubber for wiper blades of windshield wipers, and also to a coating solution and, respectively, a process for production of the wiper rubber, as in the preamble of the independent claims.
Wiper rubber profiles for wiper blades of windshield wipers are subjected to demanding mechanical requirements. By way of example, they have to provide sufficiently good wiping effect on a surface requiring cleaning, while at the same time minimizing generation of noise during the wiping process. These wiper rubber profiles moreover have to have high resistance to environmental effects, a particular example being ozone or UV radiation. In order to comply with these requirements, wiper rubber profiles are generally manufactured from a suitable elastomer material or rubber material and are surface-coated. The effect of the coating is that the coefficient of friction between wiper blade and surface requiring cleaning is reduced during the wiping process and that the wear resistance of the wiping edge, necessary for cleaning of the surface, is improved.
Conventional methods in this connection are chlorination of the wiper rubber profile, and also frequently additional application of a graphite finish. For this, graphite powder is suspended in a suitable organic solvent and sprayed onto the material at least in the region of the wiping lip of the wiper rubber. The organic solvent evaporates and the graphite particles remain finely distributed on the rubber surface and, during a wiping process, reduce the level of friction between elastomer material and surface requiring cleaning.
A disadvantage is that the graphite particles applied often do not have adequate adhesion on the material of the wiper rubber profile, and the premature release of these particles often causes a reduction in the effect of the graphite finish after a short operating time.
In order to counter said problem, DE 101 32 026 A1 describes a coating for wiper blades where a particulate solid lubricant, e.g. graphite, is suspended and applied in a suitable organic binder, e.g. a polyurethane, a polyamide or an epoxy resin. Once the binder has hardened, the graphite particles are bound on the surface of the wiper rubber profile.